Anesthesia and Hypothryoidism
-
Etiology
-
autoimmune disease (Hashimoto's thyroiditis)
thyroidectomy
radioactive iodine
antithyroid medications
iodine deficiency
failure of the hypothalamic-pituitary axis (secondary hypothyroidism)
Adult manifestations
-
weight gain
cold intolerance
muscle fatigue
lethargy
constipation
hypoactive reflexes
dull facial expression
depression
decreased heart rate, contractility, stoke volume, cardiac output
cool, mottled extremities (peripheral vasoconstriction)
pleural, pericardial, abdominal effusions
low free T4
TSH elevated in primary hypothyroidism
-
thyroid hormone administration
several days for physiologic effect
weeks until definite clinical improvement
-
extreme hypothyroidism
impaired mentation
hypoventilation
hypothermia
hyponatremia (SIADH)
CHF
more common in elderly
precipitating factors
-
infection
surgery
trauma
-
intravenous thyroid hormone, T3 or T4, as bolus + infusion
monitor ECG for ischemia and dysrhythmia
hydrocortisone 100 mg IV Q8H (possible coexisting adrenal gland suppression)
ventilatory support may be needed
Anesthetic Considerations
Preoperative
-
Postpone elective surgery until correction of severe hypothyroidism (T4 < 1 mg%) or myxedema coma
Slow gastric emptying
Prone to drug-induced respiratory depression
Continue usual thyroid hormone
-
Susceptible to induction hypotension with most agents
If refractory hypotension, consider
-
additional adrenal insufficiency
CHF
Inhalation induction faster with decreased cardiac output
No significant effect on MAC
Large tongue
Other potential problems
-
hypoglycemia
anemia
hyponatremia
hypothermia
-
Delayed emergence/recovery
-
hypothermia
respiratory depression
slowed drug biotransformation
Ketorolac
